Fertilizers are responsible for over half of global food production, but there are areas in world with nutrient deficiency and other areas of nutrient excess.
Managing mineral plant nutrients requires careful application of science and skill to meet production, environmental, and social goals.

Sunday, December 2, 2012

Re-evaluate your potash application- getting enough?

Nutrient removal without replacement

In many Western soils, the
importance of maintaining adequate levels of potassium is frequently
overlooked. The rocks and minerals that
formed many of the soils in this region were naturally high in potassium. When these soils were first farmed, there was
little response to added potassium in many cases.

Continuous cultivation requires nutrient replacement

Many years of high-yielding
crop production has resulted in a mining of this resource.For example, an alfalfa hay yield of 8 tons/A
will remove about 500 lbs K2O each year.A 400 cwt/A yield of potatoes accumulates
over 400 lb K2O/A in the plant!When high-yielding crops are continually harvested and removed from the
field, the native potassium resource finally becomes depleted and
exhausted.Even where some
potassium-rich minerals remain in the soil, they frequently cannot release
their nutrients at a rate to meet the peak demand periods of a rapidly growing
plant.

All plants require potassium

A recent study examined the
extent of potassium depletion in the Western U.S. (the balance between soil K
removal by crops and replacement with potash fertilizer).

• Arizona4.4
times more removal than replacement

• California2.0 more removal

• Idaho4.3 times more removal•Montana6.8 times more removal

• Oregon2.2 times more removal•Utah5.2 more removal

•Washington2.6 times more
removal• Wyoming9.2 times more removal

It is clear that on average
in every Western state, we are rapidly depleting soil potassium reserves.While these averages do not represent every
specific field, the overall trend simply cannot continue indefinitely if we
want to maintain our current yields.

Potassium-deficient lettuce

Inside the plant, potassium
is vitally important for many enzymes involved in photosynthesis, organic
compound synthesis, translocation of important plant materials, and maintaining
proper water balance.Since potassium is
mobile in the plant, deficiency symptoms appear first on the oldest leaves as
yellowing around the leaf margin or specks between the leaf veins.However, once deficiency symptoms are
visible, plant growth has already declined and the crop continues to lose yield
each day.

High-yielding Idaho potatoes

Regular soil testing is the
best way to predict the amount of potassium available for next year’s crop and decide
on appropriate nutrient replacement rates.If this is not possible, keep in mind the amount of potassium removed in
past crops and in the coming year.Don’t
wait until deficiencies occur before replenishing the supply of this essential
plant nutrient with potassium fertilizer.

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About Me

I am a soil scientist with interest in managing plant nutrients in the best way possible. I am fortunate to be able to work in research and education to be able to accomplish this goal.
After receiving a PhD in Soil Science at the University of California (Riverside), I worked as a Research Scientist for the U.S. government, as a Professor of Soil Science, and now I work for a not-for-profit institution. It's been a wonderful experience!